// 反转字符串
/**
 * @param {character[]} s
 * @return {void} Do not return anything, modify s in-place instead.
 */
 var reverseString = function(s) {
    let n=s.length;
    for(let l=0, r=n-1;l<r;l++,r--){
      [s[l], s[r]] = [s[r], s[l]];  
    }
    };